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1,\(3x-1=0\Leftrightarrow3x=-1\Leftrightarrow x=-\dfrac{1}{3}\)
2,\(2-x=3x+1\Leftrightarrow2-1=3x+x\rightarrow1=4x\Rightarrow x=-\dfrac{1}{4}\)
3,\(2\left(x-2\right)-1=5x\Leftrightarrow2x-4-1=5x\Leftrightarrow2x-5x=4+1\Rightarrow3x=5\Rightarrow x=\dfrac{5}{3}\)
4,\(\dfrac{x}{3}-\dfrac{x}{5}=4\Leftrightarrow\dfrac{5x}{15}-\dfrac{3x}{15}=\dfrac{60}{15}\Rightarrow5x-3x=60\Rightarrow2x=60\Rightarrow x=\dfrac{60}{2}=30\)
`20((x-2)/(x+1))^2-5((x+2)/(x-1))^2+48(x^2-4)/(x^2-1)=0(x ne +-1)`
Đặt `(x-2)/(x+1)=a,(x+2)/(x-1)=b`
`pt<=>20a^2-5b^2+48ab=0`
`<=>20a^2+48ab-5b^2=0`
`<=>20a^2-2ab+50ab-5b^2=0`
`<=>2a(a-10b)+5b(10a-b)=0`
`<=>(a-10b)(2a+5b)=0`
Đến đây dễ rồi bạn tự giải tiếp.
ĐKXĐ: x \(\ne\)\(\pm\)1
Ta có: \(20\left(\dfrac{x-2}{x+1}\right)^2-5\left(\dfrac{x+2}{x-1}\right)^2+48\cdot\dfrac{x^2-4}{x^2-1}=0\)
Đặt: \(\dfrac{x-2}{x+1}=a\) ; \(\dfrac{x+2}{x-1}=b\)
=> ab = \(\dfrac{x^2-4}{x^2-1}\)
Do đó, ta có pt mới: 20a2 - 5b2 + 48ab = 0
<=> 20a2 + 50ab - 2ab - 5b2 = 0
<=> (10a - b)(2a + 5b) = 0
<=> \(\left[{}\begin{matrix}10a=b\\2a=-5b\end{matrix}\right.\)
TH1: 10a = b => \(10\cdot\dfrac{x-2}{x+1}=\dfrac{x+2}{x-1}\)
<=> 10(x - 2)(x - 1) = (x + 2)(x + 1)
<=> 10x2 - 30x + 20 = x2 + 3x + 2
<=> 9x2 - 33x + 18 = 0
<=> 9x2 - 27x - 6x + 18 = 0
<=> (9x - 6)(x - 3) = 0
<=> \(\left[{}\begin{matrix}x=3\\x=\dfrac{2}{3}\end{matrix}\right.\)(tm)
TH2: \(2a=-5b\)=> \(2\cdot\dfrac{x-2}{x+1}=-5\cdot\dfrac{x+2}{x-1}\)
=> (2x - 4)(x - 1) = (-5x - 10)(x + 1)
<=> 2x2 - 6x + 4 = -5x2 - 15x - 10
<=> 7x2 + 9x + 14 = 0
=> pt vn
1: =>2(x+2)>3x+1
=>2x+4-3x-1>0
=>-x+3>0
=>-x>-3
=>x<3
2: =>12x^2-2x>12x^2+9x-8x-6
=>-2x>-x-6
=>-x>-6
=>x<6
3: =>4(x+1)-12>=3(x-2)
=>4x+4-12>=3x-6
=>4x-8>=3x-6
=>x>=2
4: =>-5x<=15
=>x>=-3
5: =>3(x+2)-5(x-2)<30
=>3x+6-5x+10<30
=>-2x+16<30
=>-2x<14
=>x>-7
6: =>5(x+2)<3(3-2x)
=>5x+10<9-6x
=>11x<-1
=>x<-1/11
